There are various types of braces and casts that are used to protect a portion of a body during recovery. Braces are used to limit the movement of a joint and are useful in preventing injury or allowing a joint to heal by preventing movement correlating with the injury. Common braces are elastic which are made of stretch materials or hinged which include some hard components. Elastic braces are frequently made from woven materials such as cotton, Lycra, nylon or other blends that provide exceptional breathability and wearing comfort. These braces conform to the elbow, wrist, leg and knee providing a natural freedom of movement. Braces are typically off the shelf items that are secured to the patient's body with straps. The brace can have pads or other cushioning which are placed between the patient's body and the more rigid brace structures. Flexible off the shelf braces offer inexpensive modalities for restriction of motion and added support of targeted body parts. However, the use of flexible materials and generic sizing limits the amount of control that the off the shelf brace can provide. For a given individual the “off the shelf” braces offer limited conformability. The axis of rotation is not accurately placed relative to the native joint axes and is less useful for clinical range of motion bracing situations that demand greater accuracy in position, conformation, and control of motion.
Hinged braces usually offer greater support and stability than elastic or neoprene braces. Hinged braces are a subset of range of motion braces. For the rehabilitation or treatment of many diarthrodial joints such as the knee, and elbow, motion is required early after injury, surgery or treatment to achieve a good clinical and functional result. Motion braces provide support to the injured joints while allowing for controlled motion in the proper planes with restriction of motion established by the health care provider. Without early motion, stiffness results with reduction in the long term range of motion and suboptimal clinical results. Hinged knee braces are examples of dynamic braces that move in order to provide increased support of knee joints following an injury or after surgery. Hinged knee braces are used for treatment of ligamentous injuries within the knee or on a perioperative basis. They are most frequently used for the treatment of anterior cruciate ligament injuries and medial collateral ligament injury in the knee. These braces are also used in a protective basis by athletes post injury and on a prophylactic basis such as football linemen, who wear the braces on a routine basis for protection. Rehabilitative removable knee braces are also available as range of motion braces. These braces have hinges incorporated into the brace that can specify and limit the degrees of motion in both flexion and extension. These can also be locked into full extension with a “drop lock” mechanism. These range of motion braces are used frequently in a trauma or reconstructive setting in which the range of motion must be advanced in a controlled setting. Other dynamic splints offer additional stress applied to the joint to achieve increased motion in the setting of joint contractures. These braces apply and additional force at the extremes of motion to assist in stretching out the joint.
In contrast to a brace or a splint, a cast is typically a circumferential device used to immobilize and protect a limb or body part. An orthopedic cast is a circumferential shell, frequently made from plaster or fiberglass, encasing a limb or, in some cases, large portions of the body to hold a broken bone or bones in place to allow healing. Upper extremity casts are those which encase the arm, wrist, and/or hand. A long arm cast encases the arm from the hand to about 2 inches below the arm pit, leaving the fingers and thumbs free. A short arm cast, in contrast, stops just below the elbow. Both varieties may, depending on the injury and the doctor's decision, include one or more fingers or the thumb, in which case it is called a finger spica or thumb spica cast. Lower extremity casts are classified similarly, with a cast encasing both the foot and the leg to the thigh being called a long leg cast, while one covering only the foot and the lower leg below the knee is called a short leg cast. A walking heel may be applied, or a canvas, leather or rubber cast shoe provided to the patient who is expected to walk on the immobilized limb during convalescence (referred to as being weight bearing). Where the patient is not to walk on the injured limb, crutches or a wheelchair may be provided. The sole of a leg cast may also be extended to the tip of the toes, if providing a toeplate. This addition may be made to offer support to and stabilize the metatarsals and to protect the toes from additional trauma. This is a common treatment for a broken foot. In some cases, a cast may include the upper and lower arm and the elbow, but leaves the wrist and hand free, or the upper and lower leg and the knee, leaving the foot and ankle free. Such a cast may be called a cylinder cast, or may simply be called a long arm or long leg cast.
Orthopedics casts are typically single use, non removable devices that are circumferentially applied to the patient and are not intended to be removed by the patient. Typically, any removal of the cast disrupts the conformity of the underlying cotton layer and leads to the replacement of the device. Immobilization devices in which the structural components are non circumferential are referred to as splints. These typically apply rigidity to a portion of the body part but allow motion, expansion or adjustment in other planes.
Casts are typically applied by physician or cast technician in layers. The body part which will receive the cast is initially covered with a thin woven cotton layer or stockinette. The part is then overwrapped with thin loose cotton wrap such as Webril that is applied in layers. An attempt is made to apply the cotton as uniformly as possible as any folds or imperfection can be a source of future skin breakdown once the hard outer shell is applied. Typically greater amounts of the cotton padding layer are applied over the terminal regions for the cast. Bony prominences also receive additional padding. Once the padding is applied, the body part is wrapped in either plaster of fiberglass. These materials are self setting and are activated by immersing in water prior to wrapping around the body part. Casts are circumferential devices and the plaster/fiberglass is applied as a wrap around the body part. The physician then applies a mold to the cast in an attempt to make the cast conform and support the body part in the critical planes. For example in the treatment of a fracture, typically a 3 point mold is applied in the plane of likely collapse or deformation of the fracture, to prevent displacement. As the cast is circumferential, hoop stresses tend to expand the cast dimensions in the planes orthogonal to the mold. Control of the casting depends on the skill of the practitioner, the amount of padding applied, the amount of tension on the materials and the appropriate molding of the cast during the setting process. Once the cast has set, the cast may be trimmed and additional padding may be applied to the edges if necessary to address sharp edges.
Imperfect application of the cast is associated with multiple complications including skin breakdown, discomfort, emergency room visits, compartment syndromes, loss of fixation or fracture reduction, malunion of fractures, need for surgical intervention, nerve injury, vascular injury. Revision of casts with removal and application of new casts is a frequent occurrence and is associated with significant cost and patient morbidity.
Body casts, which cover the trunk of the body and in some cases the neck up to or including the head or one or more limbs, are rarely used today for adults, but continue to be used commonly for the treatment of pediatric conditions. A body cast encases the trunk of the patient's body, and may have sections that extend over the shoulders. The body cast is usually referred to as a body jacket. A cast which includes the trunk of the body and one or more limbs and a cast which includes the “trunk” of the arm and one or more fingers or the thumb are called a spica cast. For example, a shoulder spica cast includes the trunk of the body and one arm, usually to the wrist or hand. Shoulder spica casts are used less frequently today, having been replaced with specialized splints and slings which allow early mobility of the injury so as to avoid joint stiffness after healing. A hip spica cast includes the trunk of the body and one or more legs. A hip spica cast which covers only one leg to the ankle or foot may be referred to as a single hip spica, while one which covers both legs is called a double hip spica. A one-and-a-half hip spica cast encases one leg to the ankle or foot and the other to just above the knee. The extent to which the hip spica covers the trunk depends greatly on the injury and the surgeon. For example, the spica cast may extend only to the navel, allowing mobility of the spine and the possibility of walking with the aid of crutches, or it may extend to the rib cage or even to the armpits in some rare cases. Hip spica casts were formerly common in reducing femoral fractures, but today they are used commonly for the treatment of pediatric hip conditions. In some cases, a hip spica cast may only extend down one or more legs to above the knee. Such casts, called pantaloon casts, are used to immobilize an injured lumbar spine or pelvis, in which case the trunk portion of the cast usually extends to the armpits.
Body casts are typically applied with use of a special frame and the use of multiple technicians or physicians. The patients may require sedation if adults. Body casts or hip spica casts applied to pediatric patients usually require general anesthesia and the casts are applied in the operating room. The body and hip spica casts are typically worn for extended duration of 6 to 12 weeks. Excessive cost and morbidity is associated with the need to replace the device. Hygiene is a difficult problem for pediatric spica casts as soilage of the brace is a frequent occurrence. The need for a general anesthetic to replace the cast is a strong disincentive to change the cast for anything other than a medical reason.
Other body casts which were used to protect an injured spine or as part of the treatment for a spinal deformity such as scoliosis include the Minerva cast and Risser cast. The Minerva cast includes the trunk of the body (sometimes extending down only so far as the rib cage) as well as the patient's head, with openings provided for the patient's face, ears, and usually the top of the head and hair. The Risser cast was similar, extending from the patient's hips to the neck and sometimes including part of the head.
Casts are frequently made from plaster, encasing the limb and/or body. Plaster bandages consist of a cotton bandage that has been impregnated with plaster of paris, which hardens after it has been made wet. Alternatively, bandages made of synthetic materials are often used in casts. For example, casts are often made of knitted fiberglass bandages impregnated with polyurethane, sometimes bandages of thermoplastic. These synthetic material casts are lighter and dry much faster than plaster casts.
Because the casts are applied directly to the patient's body, they have a custom fit. In contrast, most braces for common medical injuries or conditions are off the shelf items that are adjusted to fit the patient. For more severe injuries, chronic conditions or perioperative immobilization, greater brace control and conformity is required. These patients require the use of custom braces that are frequently produced by specialists such as prosthetists and orthotists. These specialists typically either take a mold of the patient from which they can produce a positive model of the patient. Around this positive mold, the prosthetist can then wrap materials and construct a custom device. The amounts of padding and reinforcement are based on the clinical experience of the orthotist and the “art” of brace manufacturing. When custom prosthetics, braces and orthotics are designed, medical practitioners frequently rely on their hands to feel the patient's soft tissue and bone structure. The practitioners identify bony protuberances that they feel under the tissue and mark these locations as landmarks reference points that they can then use to create the custom device for the body. The practitioners work on an iterative basis with the patient and the models of the patient to create a brace that conforms to the patient yet has the proper padding and support necessary for its clinical use.
There are many limitations to the traditional methods of brace production. The entire process is very labor intensive and inefficient. The limitations of the method of sizing and manufacture have limited the end product. Manufacturing restrictions have limited the choice of designs, and the functionality of the end product. The custom devices are labor intensive and they are limited in geometric complexity. The custom devices can also be highly inaccurate since they are hand made and may only vaguely represents the patient's body. The hand made process also does not allow for special adjustments to the custom device, which may include clearances, or custom windows for tender spots, rashes, birthmarks, moles, nipples, stitches, bruises, or other areas on the skin that may require special clearance or avoidance. What is needed is an improved system and method for designing braces that are more accurately fitted to the patient, thinner, stronger, more comfortable and selectively flexible.